Enhanced data link communication over iridium

ABSTRACT

A method to reduce latency in a data link communication is provided. The method includes compressing a data packet to be uplinked from a ground station to an aircraft communications addressing and reporting system (ACARS) in an aircraft and determining a packet size of the data packet. The aircraft communications addressing and reporting system is configured to receive packets having a packet size less than or equal to a first threshold packet size. An Iridium router based unrestricted digital inter-working connectivity solution data service is implemented to uplink the compressed data packet if the packet size exceeds a second threshold packet size. A short burst data service is implemented to uplink the compressed data packet if the packet size is less than or equal to the second threshold packet size.

RELATED APPLICATION

The present application is a continuation application of U.S.application Ser. No. 12/233,785, filed on Sep. 19, 2008, the disclosureof which is incorporated herein by reference.

BACKGROUND

Data link communication systems transmit messages between aircraft andground stations via radio or satellite. A network of ground radiostations ensure that aircraft can communicate with ground in real-timefrom practically anywhere in the world. Satellites are used over oceansor remote areas were no ground stations exist. Aircraft communicationsaddressing and reporting system (ACARS) is a data link system thathandles text-based information of essentially the same type as can besent via ground-ground telex. A person or a system on board creates amessage and sends it via ACARS to a system or user on the ground andvice versa. Messages are sent both automatically and manually.

There are three major components to the ACARS data link system: aircraftequipment, service providers, and ground processing systems. An ACARScommunications management unit (CMU or MU) is on board the aircraft. TheMU is connected to a number of other devices on board the airplane: avery high frequency (VHF) radio, a keyboard and display for the pilotmaster control display unit (MCDU) and a printer. In some cases, the CMUis also connected to other systems.

The data link service provider delivers a message from the aircraft tothe ground station, and vice versa. The data link service provideroperates a network of ACARS VHF remote ground stations (RGSs). Serviceproviders also provide service via SATCOM and HF data link as analternative to VHF to provide full data link capability also in remoteareas or over oceans.

The ground processing system, such as Honeywell's global data centre(GDC), performs all data link-specific tasks, maintains connection withservice providers, logs messages, etc. The ground processing system'sdata link application, such as, weather information and flight planningengine, is connected to back-end computer systems at the groundprocessing system. The ground processing system and ACARS togetherprovide real-time communication between the ground and aircraft.

There are technical limitations of currently available data linkcommunications. The ACARS data link is limited by a low-speed air/groundVHF link. Messages must be kept short, since the delivery performancedecreases exponentially with message size. The maximum block size of thedata link message for the ACARS data link is 220 characters or less. Theaverage real-life performance has an end-to-end delivery time of 10-20seconds in the uplink message, and 5-10 seconds in the downlink message.In the case of multi-block uplinks, the system experiences high latency.

Current AirSat II Iridium satellite communication systems are designedto establish connection to ACARS communications management unitsallowing the transfer of information to and from the ground processingsystem, such as Honeywell Global Data Center, using the standardAirborne Flight Information System (AFIS) protocol. The AFIS protocolhas a limit on message size that can be datalinked.

SUMMARY

The present application relates to a method to reduce latency in a datalink communication. The method includes compressing a data packet to beuplinked from a ground station to an aircraft communications addressingand reporting system (ACARS) in an aircraft and determining a packetsize of the compressed data packet. The aircraft communicationsaddressing and reporting system is configured to receive packets havinga packet size less than or equal to a first threshold packet size. Themethod implements an Iridium router based unrestricted digitalinter-working connectivity solution data service to uplink thecompressed data packet if the packet size exceeds a second thresholdpacket size, and implements a short burst data service to uplink thecompressed data packet if the packet size is less than or equal to thesecond threshold packet size.

DRAWINGS

FIG. 1 shows an uplink of messages in a data link communication systemin accordance with an embodiment of the present invention;

FIG. 2 shows a flow diagram for the uplink of messages and downlink ofacknowledgements in the data link communication system in accordancewith an embodiment of the present invention;

FIG. 3 is a flow diagram of a method to reduce latency in a data linkcommunication system while uplinking data packets of increased packetsize from a ground station to an aircraft in accordance with anembodiment of the present invention;

FIG. 4 is a flow diagram of a method to reduce latency in a data linkcommunication system while uplinking data packets of increased packetsize within an aircraft in accordance with an embodiment of the presentinvention;

FIG. 5 shows a downlink of messages in an embodiment of a data linkcommunication system in accordance with the present invention;

FIG. 6 is a flow diagram of a method to reduce latency in a data linkcommunication while downlinking data packets of increased packet sizefrom an ACARS in an aircraft to a ground station in accordance with anembodiment of the present invention;

FIG. 7 shows a flow diagram for the downlink of messages and uplink ofacknowledgements in the data link communication system in accordancewith an embodiment of the present invention; and

FIG. 8 shows an aircraft having an Iridium satellite transceiver and anACARS in accordance with an embodiment of the present invention.

In accordance with common practice, the various described features arenot drawn to scale but are drawn to emphasize features relevant to thepresent invention. Like reference characters denote like elementsthroughout figures and text.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown byway of illustration specific illustrative embodiments in which theinvention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention, and it is to be understood that other embodiments may beutilized and that logical, mechanical and electrical changes may be madewithout departing from the scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense.

Embodiments of data link communication systems described herein transmitmessages (referred to herein as data packets) between aircraft andground stations via an Iridium satellite, in which the message size isincreased while the system latency is maintained or reduced. Embodimentsof the methods to reduce latency in a data link communication describedherein permit a compressed (or uncompressed) data packet to be sent froma ground station to an aircraft housing the aircraft communicationsaddressing and reporting system via an Iridium satellite, even if thecompressed (or uncompressed) data packet has a packet size greater thanthe packet size that the aircraft communications addressing andreporting system (ACARS) can receive. The data packet is multi-blockedinto packets at an Iridium satellite transceiver in the aircraft, asnecessary, so the packets sent from the Iridium satellite transceiver tothe ACARS are of acceptable packet size at the ACARS.

Embodiments of the methods to reduce latency in a data linkcommunication described herein permit a compressed (or uncompressed)data packet to be sent from an aircraft housing the aircraftcommunications addressing and reporting system via an Iridium satelliteto a ground station, even if the compressed (or uncompressed) datapacket has a packet size greater than the packet size that the aircraftcommunications addressing and reporting system (ACARS) can send. Thepackets or blocks for a message to be downlinked are received from theACARS at the Iridium satellite transceiver, formed into a data packet atthe Iridium satellite transceiver, and compressed (or not in someembodiments) so the data packet sent from the Iridium satellitetransceiver to the ground station has a packet size greater than thepacket size that the aircraft communications addressing and reportingsystem (ACARS) can send.

FIG. 1 shows an uplink of messages in a data link communication system10 in accordance with an embodiment of the present invention. The datalink communication system 10 is an ACARS based system. Thus, the datalink communication system 10 is operable to increase the bandwidth anddata service of the ACARS 70 on board an aircraft 50 by compressing thedata being data-linked, by increasing the data link message block size,and by intelligently selecting either a short burst data (SBD) serviceor an Iridium router based unrestricted digital inter-workingconnectivity solution (RUDICS) data service. The intelligent selectionof SBD service or an RUDICS data service is based on the size of themessage, type of message, and type of uplink/downlink (that is,multi-block or single block).

The data link communication system 10 includes a ground station 200, anIridium satellite 100, and an Iridium satellite transceiver 60 and ACARS70 positioned in an aircraft 50. The Iridium satellite transceiver 60includes software 61 located in a storage medium 130. The ground station200 houses a data link service provider (DSP) 205 including software 221located in storage medium 210. The software 221 in the data link serviceprovider 205 in the ground station 200 and the software 61 in theIridium satellite transceiver 60 modify all messages to be uplinked(uplinked messages) transmitted from the ground station 200 to theaircraft 50 that are longer than a first threshold packet size. In oneimplementation of this embodiment, the first threshold packet size is220 bytes. In another implementation of this embodiment, the firstthreshold packet size is other than 220 bytes. The software 61 in theIridium satellite transceiver 60 modifies all messages to be downlinked(downlink messages) transmitted from the aircraft 50 to the groundstation 200 that are longer than a first threshold packet size. Thismessage modification advantageously implements the capability of theIridium satellite 100 in order to reduce the latency of the data linkcommunication system 10. The modifications of the uplinked anddownlinked messages are based on the size of the message, the type ofmessage, and the type of uplink/downlink (i.e., multi-block or singleblock) as described herein.

The Iridium satellite transceiver 60 and the Iridium satellite 100 areenabled for SBD service and for RUDICS data service. The Iridiumsatellite transceiver 60 is communicatively coupled to the co-locatedACARS 70, which includes an ACARS communications management unit (CMU)75. In one implementation of this embodiment, the ACARS 70 includes anACARS management unit (MU). The Iridium satellite transceiver 60 iscommunicatively coupled to the aircraft antenna 52. The aircraft antenna52 is communicatively coupled to the Iridium satellite 100 viacommunication links 252 and 253 (uplink and down link, respectively).The Iridium satellite 100 is communicatively coupled to the groundstation 200 via communication links 251 and 254 (uplink and down link,respectively). In this manner, the Iridium satellite transceiver 60 iscommunicatively coupled to the ground station 200.

The communication links 252 and 253 are shown as separate communicationlinks for ease of viewing but in some embodiments they are the samewireless communication link. Likewise, the communication links 251 and254 are shown as separate communication links but in some embodimentsthey are the same wireless communication link.

SBD is an efficient, packet-based service for frequent short datatransmissions that typically are less than 500 bytes per transfer. TheSBD service supports 1960 bytes Mobile Originated data packet (i.e.,downlink data packet) and 1890 bytes Mobile Terminated data packet(i.e., uplink data packet). In SBD-based data transfer, the packetswitching opens the connection just long enough to send a data packetand then closes. RUDICS is a circuit switched data service designed fortransfer of data packets that typically are 500 bytes or more pertransfer. In RUDICS-based data transfer, the packet switching opens aconnection and keeps it open until the last bit of data for the sessionis sent. The circuit is pre-defined before the connection is made.

The processors 65 and 235 execute software 61 and 221, respectively,and/or firmware that causes the processors 65 and 235 to perform atleast some of the processing described here as being performed by theIridium satellite transceiver 60 and data link service provider 205,respectively. The software 61 and 221 and/or firmware executed by theprocessors 65 and 235, respectively, comprise a plurality of programinstructions that are stored or otherwise embodied on a storage media130 and 210, respectively, from which at least a portion of such programinstructions are read for execution by the processors 65 and 235,respectively. In one implementation, the processors 65 and 235 comprisea microprocessor or microcontroller. In another implementation, theprocessors 65 and 235 comprise processor support chips and/or systemsupport chips such as application-specific integrated circuits (ASICs).

As described above, the ACARS 70 is programmed to accept only messageswith a packet size of 220 bytes or less while the Iridium satellitetransceiver 60 is able to receive messages with a packet size greaterthan 220 bytes. The Iridium satellite transceiver 60 multi-blocks themessages with packet size greater than 220 bytes to increase the latencyof the data link system 10. As defined herein a “length in bytes of adata packet” is the “packet size.”

FIG. 2 shows a flow diagram for the uplink of messages and downlink ofacknowledgements in the data link communication system 10 in accordancewith an embodiment of the present invention. A data packet 280 (completeACARS message) is generated at the data link service provider 205(FIG. 1) and transmitted via communication link 271 to the Iridiumsatellite. In one implementation of this embodiment, the processor 235executes software 221 stored in the storage medium 210 of the data linkservice provider 205 to compress the data packet 280. The methodsdescribed herein include the steps of compression/decompression but oneskilled in the art can understand how to implement the methods describedherein without the steps of compression/decompression after reading thisdocument.

An exemplary case for a data packet 280 is compressed to X bytes inlength (X is an integer) is now described. If X is less than or equal toa second threshold packet size, such as 1890 bytes (i.e., compresseddata packet 280 is less than or equal to 1890 bytes in length), theprocessor 235 then executes software 221 to configure the data packet280 for SBD transmission. If X is greater than the second thresholdpacket size 1890 (i.e., compressed data packet 280 is greater than 1890bytes in length), the processor 235 then executes software 221 toconfigure the compressed data as an uplinked data packet 280 for RUDICStransmission. In one implementation of this embodiment, 1890 bytes is asecond threshold packet size. In another implementation of thisembodiment, the second threshold packet size is different from 1890bytes.

The compressed data packet 280 transmitted from the ground antenna 202is received at the Iridium satellite 100 over communication link 251.The Iridium satellite 100 sends the received data packet viacommunication link 252 to the aircraft 50. The communication links 251and 252 in FIG. 1 are represented generally as a single communicationlink 271 in FIG. 2. The compressed data packets 280 received at theIridium satellite transceiver 60 are decompressed by the Iridiumsatellite transceiver 60. If the decompressed data packet exceeds thefirst threshold packet size, such as 220 bytes, the data packet issegmented into a plurality of blocks 281(1-N) (ARINC 618 multi-block formessage to be uplinked). The blocks 281(1-N) are also referred to hereinas “packets 281(1-N).” Each of the plurality of blocks 281(1-N) has apacket size less than or equal to 220 bytes in length. Specifically, theprocessor 65 executes the software 61 in the Iridium satellitetransceiver 60 to decompress the data in the data packet 280 and tomulti-block any decompressed data packet 280 that exceed 220 bytes into220 byte blocks 281(1-N). In this manner, the data packet 280 isreformed as blocks 281(1-N) and the blocks 281(1-N) are sent to theACARS 70 while the data link communication system 10 has reduced thesystem redundancy.

The number N of blocks 281(1-N) of 220 bytes is (X/220), where the(X/220) is rounded up to the next higher integer when (X/220) is not aninteger. Thus, when the number (X/220) is an integer, all the packetshave a packet length of 220 bytes. When the number (X/220) is not aninteger, X/220 is rounded up to the next higher integer and the lastblock 281-N has a packet length of less than 220 bytes. Themulti-blocked messages are sent to the ACARS 70 via communication link255. The blocks 281(1-N) sent over communication link 255 are of packetsizes that are acceptable by the ACARS 70 for processing by thecommunication management unit 75. Since the data packet 280 istransmitted from the ground station to the aircraft 50 with a packetsize greater than the first the threshold packet size (for example, 220bytes), the system latency for the data link communication system 10 isreduced.

For each block 281(1-N) received at the ACARS 70, a respective localacknowledgement 282(1-N) is sent via communication link 256 to theonboard Iridium satellite transceiver 60. The local acknowledgments282(1-N) are stored in the Iridium satellite transceiver 60 untilacknowledgements 282(1-N) are received for all the blocks 281(1-N). Onceall the acknowledgements 282(1-N) are received, the Iridium satellitetransceiver 60 re-blocks the plurality of local acknowledgements282(1-N) to generate a single acknowledgement 283. The singleacknowledgement 283 is sent to the Iridium satellite 100 viacommunication link 253 and from the Iridium satellite 100 to the groundstation 200 via communication link 254. The communication links 253 and254 in FIG. 1 are shown as 272 in FIG. 2. In one implementation of thisembodiment, the local acknowledgements 282(1-N) are stored in memory 62in the Iridium satellite transceiver 60. In another implementation ofthis embodiment, the memory is part of the processor 65. In yet anotherimplementation of this embodiment, the re-blocked single acknowledgementis compressed to form a compressed acknowledgement. The Iridiumsatellite transceiver is configured to implement the Iridium routerbased unrestricted digital inter-working connectivity solution dataservice to downlink the acknowledgement, if the packet size of thesingle acknowledgement is greater than a third threshold packet size,such as 1960 bytes.

In one implementation of this embodiment, the data packet 280 formedafter compression is less than 1890 bytes in length, so the data linkservice provider 205 implements the SBD service to uplink data packet280 to the Iridium satellite transceiver 60. In another implementationof this embodiment the data packet 280 formed after compression isgreater than or equal to 1890 bytes in length, so the data link serviceprovider 205 implements the RUDICS data service to uplink data packet280 of to the Iridium satellite transceiver 60.

FIG. 3 is a flow diagram of a method 300 to reduce latency in a datalink communication system 10 while uplinking data packets of increasedpacket size from a ground station 200 to an aircraft 50 in accordancewith an embodiment of the present invention. In one implementation ofthis embodiment, the data link communication system 10 is the ACARSbased system described above with reference to FIGS. 1-2. The method 300is described with reference to the link communication system 10 shown inFIG. 1 although it is to be understood that method 300 can beimplemented using other embodiments of the data link communicationsystem as is understandable by one skilled in the art who reads thisdocument.

At block 302, the data in the data packet to be uplinked from a groundstation 200 to an aircraft communications addressing and reportingsystem (ACARS) 70 in an aircraft 50 is compressed. The ACARS 70 isconfigured to receive packets (also referred to herein as “blocks”)having a packet size less than or equal to a first threshold packetsize. In one implementation of this embodiment, the first thresholdpacket size is 220 bytes. The data packet 280 shown in FIG. 2 is anexemplary compressed data packet. At block 304, the data link serviceprovider 205 determines the packet size of the compressed data packet,such as data packet 280. At block 306, it is determined if a packet sizeof the compressed data packet 280 to be uplinked from a ground station200 to an aircraft communications addressing and reporting system(ACARS) 70 in an aircraft 50 exceeds a second threshold packet size.Specifically, the data link service provider 205 determines if thepacket size of the compressed data packet 280 is greater than the secondthreshold packet size. If the packet size is less than or equal to thesecond threshold packet size, the flow proceeds to block 308 and a shortburst data service is implemented to send the compressed data packet tothe aircraft 50. If the packet size is greater than the second thresholdpacket size, the flow proceeds to block 310. At block 310, the Iridiumrouter based unrestricted digital inter-working connectivity solutiondata service is implemented to send the compressed data packet 280 tothe aircraft 50.

FIG. 4 is a flow diagram of a method 400 to reduce latency in a datalink communication system 10 while uplinking data packets of increasedpacket size within an aircraft 50 in accordance with an embodiment ofthe present invention. In one implementation of this embodiment, thedata link communication system 10 is the ACARS based system describedabove with reference to FIGS. 1-2. The method 400 is described withreference to the link communication system 10 shown in FIG. 1 althoughit is to be understood that method 400 can be implemented using otherembodiments of the data link communication system as is understandableby one skilled in the art who reads this document. The method 400 isimplemented after the process of block 308 or 310 is implemented, asdescribed above with reference to FIG. 3, and a data packet is sent tothe Iridium satellite transceiver 60 via communication link 251, theIridium satellite 100, and communication link 253.

At block 402, the compressed data packet received at Iridium satellitetransceiver 60 in the aircraft 50 from a ground station 200 isdecompressed. In one implementation of this embodiment, the packet sizeof the compressed data packet is greater than a first threshold packetsize. At block 404, it is determined if the packet size is greater thanthe first threshold packet size. In one implementation of thisembodiment, it is determined if the packet size is greater than 220bytes. If the packet size is less than or equal to the first thresholdpacket size, the flow proceeds block 406 and the data packet is sent toACARS 70. If the packet size is greater than the first threshold packetsize, the flow proceeds block 408. At block 408, the decompressed datapacket is multi-blocked into a plurality of blocks, so the number ofbytes in each block is less than or equal to the first threshold packetsize (such as 220 bytes). At block 410, each of the plurality of blocksor packets is sent to the ACARS 70 onboard the aircraft 50.

At block 412, a local acknowledgement 282-i for each i^(th) uplinkedblock is sequentially received at the Iridium satellite transceiver 60from the aircraft communications addressing and reporting system 70onboard the aircraft 50. The Iridium satellite transceiver 60 receivesall of the local acknowledgements 282(1-N). At block 414, the Iridiumsatellite transceiver 60 compiles all of the received localacknowledgements 282(1-N). When the local acknowledgements 282(1-N) foreach of the plurality of blocks 281(1-N) are compiled, block 416 isimplemented. At block 416, the Iridium satellite transceiver 60 sendsthe compiled acknowledgement as a single acknowledgement 283 to theground station 200. In one implementation of this embodiment, theIridium satellite transceiver 60 compresses the compiled acknowledgement283. In another implementation of this embodiment, the number of bytesin the single acknowledgement 283 is greater than the first thresholdpacket size.

FIG. 5 shows a downlink of messages in an embodiment of a data linkcommunication system 10 in accordance with the present invention. FIG. 5differs from FIG. 1 in that data packets are downlinked viacommunication link 264 from the Iridium satellite transceiver 60 in theaircraft 50 to the Iridium satellite 100 and via communication link 262from the Iridium satellite 100 to the ground station transceiver 230 inthe ground station 200. Likewise, an acknowledgement is sent from theground station 200 via communication link 263 to the Iridium satellite100 and via communication link 264 from the Iridium satellite 100 to theIridium satellite transceiver 60 in the aircraft 50. The communicationlinks 262 and 263, which are shown as separate communication links, area single bidirectional wireless communication link. Likewise, thecommunication links 254 and 251 in FIG. 1 are the same bidirectionalwireless communication links as communication links 262 and 263. Thecommunication links 261 and 264, which are shown as separatecommunication links, are a bidirectional single wireless communicationlink. Likewise, the communication links 252 and 253 in FIG. 1 are thesame bidirectional single wireless communication links as communicationlinks 261 and 264.

FIG. 6 is a flow diagram of a method 600 to reduce latency in a datalink communication system 10 while downlinking data packets of increasedpacket size from an ACARS 70 in an aircraft 50 to a ground station 200in accordance with an embodiment of the present invention. FIG. 7 showsa flow diagram for the downlink of messages 580 and uplink ofacknowledgements 583 in the data link communication system 10 inaccordance with an embodiment of the present invention. The method 600is described with reference to FIG. 7 and the link communication system10 shown in FIG. 5 although it is to be understood that method 600 canbe implemented using other embodiments of the data link communicationsystem as is understandable by one skilled in the art who reads thisdocument.

At block 602, a plurality of blocks 581(1-N) (ARINC 618 multi-block formessage to be downlinked) for a message to be downlinked aresequentially received at the Iridium satellite transceiver 60 onboardthe aircraft 50 from the ACARS 70. The blocks 581(1-N) are also referredto herein as “packets 581(1-N).” The plurality of blocks 581(1-N) areeach less than or equal too 220 bytes in length. The plurality of blocks581(1-N) is sent via communication link 555 (FIG. 7) to the Iridiumsatellite transceiver 60. At block 604, the Iridium satellitetransceiver 60 sends a local acknowledgement to the ACARS 70 for eachblock 581(1-N) as it is received. The local acknowledgements 582(1-N)are sent from the Iridium satellite transceiver 60 to the ACARS 70 viacommunication link 556 (FIG. 7).

At block 606, the plurality of blocks 581(1-N) in the message that aresequentially received from the ACARS 70 are compiled (also referred toherein as “re-blocked”) at the Iridium satellite transceiver 60 untilall the blocks 581(1-N) are received for the message to be downlinked.Each block 581(1-N) has a packet size less than or equal to 220 bytesand the re-blocked plurality of blocks form a data packet to bedownlinked that has more than the first threshold packet size. In oneimplementation of this embodiment, the plurality of blocks 581(1-N) isstored in the memory 62 until all the blocks 581(1-N) are received andthen the processor 65 compiles the plurality of blocks 581(1-N).

At block 608, the compiled blocks are compressed to form a data packet580 to be downlinked. In one implementation of this embodiment, thecompressed data packet 580 to be downlinked has a packet size greaterthan the first threshold packet size. In another implementation of thisembodiment, block 608 is not implemented. The Iridium satellitetransceiver 60 determines the packet size of the compressed data packet580 to be downlinked. At block 610, the Iridium satellite transceiver 60determines if the packet size of the compressed data packet 580 isgreater than a third threshold packet size. In one implementation ofthis embodiment, the third threshold packet size is 1960 bytes. Inanother implementation of this embodiment, the third threshold packetsize is different from 1960 bytes.

If the packet size of the compressed data packet 580 is less than orequal to the third threshold packet size, the flow proceeds to block612. At block 612, the Iridium satellite transceiver 60 implements theshort burst data service to downlink the compressed data packet 580 viaan Iridium satellite 100. The downlinked data packet 580 can have apacket size greater than the first threshold packet size.

If the packet size of the compressed data packet 580 is greater than thethird threshold packet size, the flow proceeds to block 614. At block614, the Iridium satellite transceiver 60 implements the RUDICS dataservice to downlink the compressed data packet. In this case, thedownlinked compressed data packet 580 has a packet size greater than thethird threshold packet size.

At block 616, the Iridium satellite transceiver 60 receives anacknowledgement 583 from the ground station 200 after the ground station200 receives the downlinked data packet 580. The Iridium satellitetransceiver 60 segments the single acknowledgement 583 into a pluralityof blocks 582(1-N). Each block 582-i is sequentially sent from theIridium satellite transceiver 60 to the ACARS 70. Each of the blocks582(1-N) is less than the first threshold packet size.

FIG. 8 shows an aircraft 51 having an Iridium satellite transceiver 60and an ACARS 70 in accordance with an embodiment of the presentinvention. The aircraft 51 includes the Iridium satellite transceiver 60communicatively coupled to an antenna 52 and the ACARS 70 as describedabove with reference to FIG. 1. As shown in FIG. 8, the communicationmanagement unit 75 in the ACARS 70 is communicatively coupled to a veryhigh frequency (VHF) radio 77, a display 79 for the pilot, a flightmanagement computer 80, aircraft condition monitoring system (ACMS) 82,satellite communications (SATCOM) 84, and a high frequency (HF) radio84. In one implementation of this embodiment, a printer and a keyboardare communicatively coupled to the communication management unit 75. Theaircraft 51 can be used to implement the methods 300, 400 and 600 in asystem with the Iridium satellite 100 and a ground station 200 as isunderstandable by one skilled in the art reading this document.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement, which is calculated to achieve the same purpose,may be substituted for the specific embodiment shown. This applicationis intended to cover any adaptations or variations of the presentinvention. Therefore, it is manifestly intended that this invention belimited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method to reduce latency in a data linkcommunication, the method comprising: compressing a first data packet tobe uplinked from a ground station to an aircraft-data-link device in anaircraft, the aircraft-data-link device configured to receive packetshaving a packet size less than or equal to a first threshold packetsize; determining a packet size of the compressed first data packet;when the packet size exceeds a second threshold packet size,transmitting the compressed first data packet over an uplink via aSATCOM communication link over a circuit switched data service thatkeeps a first connection open between the ground station and atransceiver onboard the aircraft, until the last bit of data for asession between the ground station and the aircraft-data-link device issent, to transfer the compressed first data packet having the packetsize exceeding the second threshold packet size, wherein a circuit isdefined for the first connection before the first connection is made;and when the packet size is less than or equal to the second thresholdpacket size, transmitting the compressed first data packet over theuplink via the SATCOM communication link via a packet switched dataservice that keeps a second connection between the ground station andthe transceiver open long enough to send only the compressed first datapacket having the packet size less than or equal to the second thresholdpacket size and then closes the second connection.
 2. The method ofclaim 1, further comprising: receiving the uplinked compressed firstdata packet having the packet size greater than the first thresholdpacket size at the transceiver in the aircraft; decompressing thereceived first data packet; multi-blocking the decompressed data packetinto a plurality of blocks, wherein the packet size of each block isless than or equal to the first threshold packet size; and sending theplurality of blocks to the aircraft-data-link device onboard theaircraft.
 3. The method of claim 2, further comprising: sequentiallyreceiving a local acknowledgement for each of the plurality of blocks atthe transceiver from the aircraft-data-link device; compiling thereceived local acknowledgements at the transceiver; and sending thecompiled acknowledgements as a single acknowledgement to the groundstation when the local acknowledgements for each of the plurality ofblocks are compiled.
 4. The method of claim 1, further comprising:sequentially receiving a plurality of blocks for a second data packet tobe downlinked at the transceiver onboard the aircraft from theaircraft-data-link device; locally acknowledging each block as it isreceived; compiling the plurality of blocks in the second data packetuntil all the blocks are received; compressing the compiled blocks toform a compressed second data packet to be downlinked; determining apacket size of the compressed second data packet to be downlinked; whenthe packet size of the data packet to be sent over a downlink is greaterthan a third threshold packet size, transmitting the compressed seconddata packet over the downlink via the circuit switched data service; andwhen the packet size of the compressed second data packet to be sentover the downlink is less than or equal to the third threshold packetsize, transmitting the compressed second data packet over the downlinkvia the packet switched data service.
 5. A system to enhance data linkcommunication, the system comprising: an aircraft-data-link deviceonboard an aircraft, the aircraft-data-link device configured to receivedata packets having a packet size less than or equal to a firstthreshold packet size; a transceiver onboard the aircraft, thetransceiver communicatively coupled to the aircraft-data-link device,wherein, when a packet size of a first data packet to be uplinked from aground station to the aircraft-data-link device is determined, at theground station, to be greater than a second threshold packet size, thetransceiver is configured to transmit and receive the first data packetvia a SATCOM communication link over a circuit switched data service,wherein, when the packet size of the first data packet to be uplinkedfrom the ground station to the aircraft-data-link device is determined,at the ground station, to be less than or equal to the second thresholdpacket size, the transceiver is configured to transmit and receive viathe SATCOM communication link via a packet switched data service,wherein the circuit switched service keeps a first connection openbetween the ground station and the transceiver, until the last bit ofdata for a session between the ground station and the aircraft-data-linkdevice is sent, to transfer the first data packet having a packet sizeexceeding a second threshold packet size, wherein a circuit is definedfor the first connection before the first connection is made, andwherein the packet switched data service keeps a second connectionbetween the ground station and the transceiver open long enough to sendonly the first data packet having a packet size less than or equal tothe second threshold packet size and then closes the second connection,the transceiver including a processor to execute software to: decompressthe uplinked first data packet; and if the decompressed uplinked firstdata packet has a packet size greater than the first threshold packetsize, multi-block the decompressed uplinked first data packet into aplurality of blocks, each block being less than the first thresholdpacket size, wherein the transceiver sequentially sends the plurality ofblocks to the aircraft-data-link device.
 6. The system of claim 5,further comprising at least one ground station communicatively coupledto the transceiver via a data communication channel, wherein the groundstation comprises: a data link service provider; a ground stationtransceiver communicatively coupled to the data link service provider;and a processor communicatively coupled to the data link serviceprovider.
 7. The system of claim 6, wherein the data link serviceprovider comprises a storage medium holding software executable by theprocessor in the ground station to compress data packets to be uplinkedand decompress data packets to be downlinked, and when a packet size ofa compressed data packet is greater than an uplink threshold packetsize, the processor is configured to transmit the compressed data packetover an uplink via the circuit switched data service, and when thepacket size of the compressed data packet is less than or equal to theuplink threshold packet size, the processor in the ground station isconfigured to transmit the compressed data packet over the uplink viathe packet switched data service.
 8. The system of claim 5, wherein thetransceiver is configured to input local acknowledgements for each ofthe plurality of blocks sent from the aircraft-data-link device, andwherein the processor compiles the acknowledgements by executingsoftware to re-block the local acknowledgements received from theaircraft-data-link device to form a single acknowledgement.
 9. Thesystem of claim 8, wherein the transceiver is configured so that thesingle acknowledgement is compressed, and wherein: if the packet size ofthe single acknowledgement is greater than a downlink threshold packetsize, the transceiver transmits the acknowledgement over a downlink viathe circuit switched data service: and if the packet size of the singleacknowledgement is less than or equal to the downlink threshold packetsize, the transceiver transmits the acknowledgement over the downlinkvia the packet switched data service.
 10. The system of claim 5, whereinthe transceiver is configured so that the data packet to be downlinkedis compressed, and wherein: if the packet size of the data packet to bedownlinked is greater than a downlink threshold packet size, thetransceiver transmits the data packet over a downlink via the circuitswitched data service; and if the packet size of the data packet to bedownlinked is less than or equal to the downlink threshold packet size,the transceiver transmits the data packet over the downlink via thepacket switched data service.
 11. The system of claim 5, wherein thecircuit switched data service is a high bandwidth data service and thepacket switched data service is a low bandwidth data service.
 12. Amethod to reduce latency in a data link communication, the methodcomprising: receiving a first data packet over an uplink via a SATCOMcommunication link over a circuit switched data service when a packetsize of the first data packet to be uplinked from a ground station to anaircraft-data-link device in an aircraft is determined, at the groundstation, to be greater than an uplink threshold packet size, wherein thecircuit switched data service keeps a first connection open between theground station and a transceiver onboard the aircraft, until the lastbit of data for a session between the ground station and theaircraft-data-link device is sent, to transfer the first data packethaving a packet size greater than the uplink threshold packet size,wherein a circuit is defined for the first connection before the firstconnection is made, and wherein the aircraft-data-link device isconfigured to receive data packets having a packet size less than orequal to a first threshold packet size; and receiving the first datapacket over the uplink via the SATCOM communication link via a packetswitched data service when the packet size of the first data packet tobe uplinked from the ground station to the aircraft-data-link device inthe aircraft is determined at the ground station to be less than orequal to the uplink threshold packet size, wherein the packet switcheddata service keeps a second connection open long enough to send only thefirst data packet having a packet size less than or equal to the uplinkthreshold packet size and then closes the second connection.
 13. Themethod of claim 12, wherein, receiving the first data packet over theuplink via the circuit switched data service comprises, receiving thefirst data packet over the uplink via a high bandwidth data service, andwherein, receiving the first data packet over the uplink via the packetswitched data service comprises transmitting the data packet over theuplink via a low bandwidth data service.
 14. The method of claim 12,further comprising: receiving the uplinked first data packet having thepacket size greater than the first threshold packet size at thetransceiver in the aircraft; multi-blocking the uplinked first datapacket into a plurality of blocks, wherein the packet size of each blockis less than or equal to the first threshold packet size; and sendingthe plurality of blocks to the aircraft-data-link device onboard theaircraft.
 15. The method of claim 14, further comprising: sending alocal acknowledgement for each uplinked block from theaircraft-data-link device onboard the aircraft to the transceiver;compiling the received local acknowledgements at the transceiver; andsending the compiled acknowledgements as a single acknowledgement to theground station when an acknowledgement is received at the transceiverfor each of the plurality of blocks.
 16. The method of claim 12, furthercomprising: sequentially receiving a plurality of blocks for a seconddata packet to be downlinked at the transceiver onboard the aircraftfrom the aircraft-data-link device; and locally acknowledging each blockas it is received from the aircraft-data-link device.
 17. The method ofclaim 16, further comprising: compiling the plurality of blocks for thesecond data packet to be downlinked; determining the packet size of thesecond data packet to be downlinked; when the packet size of the seconddata packet to be sent over a downlink is greater than a downlinkthreshold packet size, transmitting the second data packet over thedownlink via the circuit switched data service; and when the packet sizeof the second data packet to be sent over the downlink is less than orequal to the downlink threshold packet size, transmitting the seconddata packet over the downlink via the packet switched data service. 18.The method of claim 12, further comprising: compressing the first datapacket to be uplinked from the ground station to the transceiver;decompressing the uplinked compressed first data packet received at thetransceiver; compressing a second data packet to be downlinked from thetransceiver to the ground station; and decompressing the downlinkedcompressed second data packet received at the ground station.